Sea Defences Flashcards
(21 cards)
What are the advantages of a sea wall?
-Deflects waves
-Also acts as a barrier to prevent flooding
Disadvantages of a sea wall
-Expensive
-Likely too need repairs fairly regularly
-creates strong backwash which erodes under the sea wall
What is a groyne
Wooden or stone fences built at a right angle to the coast
Advantages of groynes
-Cheap
-Traps sediment transport by longshore drift
-Creates wider beach
-Slows waves-prevents erosion and flooding
Disadvantages of groynes
-need repairs
-Creates barrow beaches down the coast by starving them of sediment (Narrow beaches don’t protect the coast very well=erosion)
What is a gabion
Wire cages filled with rocks
What are the advantages of gabions
-Absorb wave energy
-relatively cheap
Disadvantages of gabions
-Shorter life span (corrode)
-unetractive
What is Rock armour (rip rap)
Boulder piled up along the coast
Advantages of rock armour
-Absorbed wave energy therefore reducing erosion and flooding
-Fairly cheap
Disadvantages of rock armour
Boulders can be moved around by strong waves then need to be replaced
What is beach nourishment
Sand and shingle from elsewhere (e.g. seabed) is added to the upper part of beaches
What are the advantages of beach nourishment?
Creates wide beaches which slows waves-greater protection from erosion and flooding.
What are the disadvantages of beach nourishment?
-Very expensive
-Has to be repeated
-Taking sediment from the sea bed can kill organisms like sponges and corals
What is dune regeneration?
Creating it restoring sand dunes by nourishment or by planting vegetation to stabilise the sand.
What are the Advantages of dune regeneration?
-Create a barrier between the sea and land
-Absorbs wave energy
-stabilization is cheap
What are the disadvantages of dune regeneration
-Nourishment is very expensive
-Protection is limited to a small area
What is hard engineering?
Man-made structures built to control the flow of the sea and reduce flooding and erosion
What is soft engineering?
Schemes set up using knowledge of the sea and its processes to reduce the effects of flooding and erosion
